SEGMENT INFORMATION - Revenue and Other Financial Information by Reportable Segment (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 28, 2020	Mar. 30, 2019
Segment Reporting Information [Line Items]
Revenue	$ 707,059	$ 604,569
Operating income	94,281	69,792
Depreciation and amortization	57,260	45,358
Capital expenditures	25,721	16,731
RMS
Segment Reporting Information [Line Items]
Revenue	145,996	137,172
Operating income	27,373	37,832
Depreciation and amortization	8,752	4,322
Capital expenditures	5,412	4,112
DSA
Segment Reporting Information [Line Items]
Revenue	438,683	354,197
Operating income	72,283	46,705
Depreciation and amortization	41,330	33,784
Capital expenditures	14,729	8,848
Manufacturing
Segment Reporting Information [Line Items]
Revenue	122,380	113,200
Operating income	41,112	31,499
Depreciation and amortization	6,366	5,805
Capital expenditures	$ 5,161	$ 3,606

The aggregate expense recognized in the current period that allocates the cost of tangible assets, intangible assets, or depleting assets to periods that benefit from use of the assets.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3602-108585

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The net result for the period of deducting operating expenses from operating revenues.

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The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=118956577&loc=SL49130543-203045

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
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-Section 50
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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